[Form 4] Disc Medicine, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Kevin Bitterman, a director of Disc Medicine, Inc. (ticker: IRON), reported a sale of company stock under a pre-existing trading plan. On 08/22/2025 he sold 2,287 shares of common stock pursuant to a Rule 10b5-1 trading plan dated January 31, 2025, at a weighted average price of $61.03 per share (individual sale prices ranged from $60.95 to $61.05). The reporting person says he can provide a breakdown of shares sold at each price on request.

The report shows beneficial ownership held indirectly through Atlas-related investment vehicles: 590,621 shares in Atlas Venture Opportunity Fund I, LP; 420,549 shares in Atlas Venture Opportunity Fund II, LP; and 51,000 shares in Atlas Venture Fund XII, L.P. The filer disclaims beneficial ownership of those fund-held shares except to the extent of any pecuniary interest.

Insights

Securities Analyst

TL;DR: Routine Rule 10b5-1 sale by a director with substantial indirect holdings through Atlas-managed funds; no obvious material change to control.

The filing documents a small-sale transaction of 2,287 shares executed under a documented 10b5-1 plan, indicating pre-authorized dispositions rather than opportunistic insider trading. The reported weighted average price is $61.03. Most shares noted on the form are held indirectly by Atlas-affiliated funds, and the reporting person disclaims beneficial ownership except for any pecuniary interest. From an investor disclosure standpoint this is a routine, transparent Form 4 that maintains compliance with Section 16 reporting obligations.

Corporate Governance Expert

TL;DR: Governance practices followed: trade executed under 10b5-1 plan and reporting includes standard ownership disclaimers for fund-held shares.

The filing includes the required attestation and an attorney-in-fact signature. The seller used a Rule 10b5-1 plan dated January 31, 2025, which, if properly documented, provides an affirmative defense to insider trading claims. The ownership disclosures identify layered fund structures and include standard disclaimers of beneficial ownership, limiting perceived direct control by the reporting person. No departures from routine disclosure practices are evident in the document.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Bitterman Kevin

(Last) (First) (Middle)

C/O DISC MEDICINE, INC.

321 ARSENAL STREET, SUITE 101

(Street)

WATERTOWN MA 02472

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Disc Medicine, Inc. [ IRON ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
08/22/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	08/22/2025		S(1)		2,287	D	$61.03(2)	590,621	I	See footnote(3)
Common Stock								420,549	I	See footnote(4)
Common Stock								51,000	I	See footnote(5)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Shares were sold pursuant to a Rule 10b5-1 trading plan dated January 31, 2025.

2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $60.95 to $61.05 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

3. These shares are held by Atlas Venture Opportunity Fund I, LP ("Opportunity I"). The general partner of Opportunity I is Atlas Venture Associates Opportunity I, LP ("Associates I"). Atlas Venture Associates Opportunity I, LLC ("Associates I LLC") is the general partner of Associates I. The Reporting Person is a member of Associates I LLC and disclaims beneficial ownership of such securities held by Opportunity I, except to the extent of his pecuniary interest therein, if any.

4. These shares are held by Atlas Venture Opportunity Fund II, LP ("Opportunity II"). The general partner of Opportunity II is Atlas Venture Associates Opportunity II, LP ("Associates II"). Atlas Venture Associates Opportunity II, LLC ("Associates II LLC") is the general partner of Associates II. The Reporting Person is a member of Associates II LLC and disclaims beneficial ownership of such securities held by Opportunity II, except to the extent of his pecuniary interest therein, if any.

5. These shares are held by Atlas Venture Fund XII, L.P. ("Atlas XII"). The general partner of Atlas XII is Atlas Venture Associates XII, L.P. ("Associates XII"). Atlas Venture Associates XII, LLC ("Associates XII LLC") is the general partner of Associates XII. The Reporting Person is a member of Associates XII LLC and disclaims beneficial ownership of such securities held by Atlas XII, except to the extent of his pecuniary interest therein, if any.

	/s/ Ommer Chohan, Attorney-in-Fact	08/26/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What transaction did Kevin Bitterman report on Form 4 for Disc Medicine (IRON)?

The Form 4 reports a sale of 2,287 shares of common stock on 08/22/2025 executed under a Rule 10b5-1 plan.

At what price were the shares sold in the reported transaction?

The shares were sold at a weighted average price of $61.03 per share, with individual sale prices ranging from $60.95 to $61.05.

How many Disc Medicine shares does the Form 4 show as beneficially owned after the transaction?

The filing lists indirect beneficial holdings of 590,621, 420,549, and 51,000 shares held by three Atlas-related funds; the reporting person disclaims beneficial ownership except for any pecuniary interest.

Was the sale made under a pre-arranged trading plan?

Yes. The sale was made pursuant to a Rule 10b5-1 trading plan dated January 31, 2025.

Who signed the Form 4 filing for the reporting person?

The Form 4 was signed by Ommer Chohan, Attorney-in-Fact on behalf of the reporting person on 08/26/2025.